Injectable compositions for the controlled delivery of pharmacologically active compound

ABSTRACT

The present invention provides compositions and methods for extending the release times and lowering the toxicity of pharmacologically active compounds. The compounds comprise a salt of the pharmacologically active compound with a lipophilic counterion and a pharmaceutically acceptable water soluble solvent combined together to form an injectable composition. The lipophilic counterion may be a saturated or unsaturated C 8 -C 22  fatty acid, and preferably may be a saturated or unsaturated C 10 -C 18  fatty acid. When injected into a mammal, at least a portion of the composition precipitates and releases the active compound over time. Thus, the composition forms a slowly releasing drug depot of the active compound in the mammal. Therefore, the present invention enables one to provide a controlled dose administration of the active compound for a periods of up to 15 days or even longer. Many compounds can be administered according to the present invention including, but not limited to, tilmicosin, oxytetracycline, metoprolol, fluoxetine, roxithromycin, and turbinafine.

This application claims the benefit of U.S. provisional application No.60/343,625 filed Oct. 19, 2001.

FIELD OF THE INVENTION

The present invention relates to methods and compositions for extendingthe release times and decreasing the toxicity of pharmacologicallyactive compounds.

BACKGROUND OF THE INVENTION

The following discussion of the background of the invention is merelyprovided to aid the reader in understanding the invention and is notadmitted to describe or constitute prior art to the present invention.

It is often desirable to extend the release time of an injected drug toincrease its duration of action, or to reduce its toxic effects.Formulations that are readily soluble in the body are usually absorbedrapidly and provide a sudden burst of available drug as opposed to amore desirable and gradual release of the pharmacologically activeproduct. A variety of attempts have been made to provide controlled andextended release pharmaceutical compounds, but have not succeeded inovercoming all of the problems associated with the technology, such asachieving an extended release time, maximum stability and efficacy,reduced toxicity, maximum reproducibility in preparation, and theelimination of unwanted physical, biochemical, or toxicological effectsintroduced by undesirable matrix materials.

Oxytetracycline is a widely used and useful antibiotic for treatingvarious infections in mammals. In particular it is used for treating andpreventing respiratory infections in domestic animals. There aresignificant costs associated with repeated administrations throughconventional means.

Tilmicosin is a macrolide antibiotic with two tertiary amines. It has along tissue half-life and is effective against a broad range of bacteriaand is used to treat respiratory diseases in cattle. At elevated levelstilmicosin is cardiotoxic and its use in sensitive species such as cats,goats, pigs and horses has been avoided almost entirely due to safetyreasons. The commercial product, Micotil® (Eli Lilly & Co.,Indianapolis, Ind.), is a solution of the di-phosphate salt and isdescribed in U.S. Pat. No. 5,574,020. This formulation is effective incattle, but the antibiotic is released rapidly and results in toxicityin many species, including dogs and cats.

SUMMARY OF THE INVENTION

Application Ser. No. 60/343,625, filed Oct. 19, 2001 is herebyincorporated by reference in its entirety, including all charts anddrawings.

The present invention provides compositions and methods for extendingthe release times and lowering the toxicity of pharmacologically activecompounds. The compounds comprise a salt of the pharmacologically activecompound with a lipophilic counterion and a pharmaceutically acceptablewater soluble solvent combined together to form an injectablecomposition. The lipophilic counterion may be a saturated or unsaturatedC₈-C₂₂ fatty acid, and preferably may be a saturated or unsaturated.C₁₀-C₁₈ fatty acid. When injected into a mammal, at least a portion ofthe composition precipitates and releases the active compound over time.Thus, the composition forms a slowly releasing drug depot of the activecompound in the mammal. Therefore, the present invention enables one toprovide a controlled dose administration of the active compound forperiods of up to 15 days or even longer. In preferred embodiments, thepharmacologically active compound may be tilmicosin, an antibiotic suchas oxytetracycline or doxycycline, or fluoxetine, roxithromycin,terbinafine, or metoprolol, and the lipophilic counterion may bedecanoic acid, lauric acid, oleic acid, linoleic acid, or myristic acid.In preferred embodiments, the pharmaceutically acceptable solvent isN-methyl pyrrolidone (NMP). In another embodiment, the pharmaceuticallyacceptable solvent is propylene glycol (e.g., at about 10%) in glycerolformal, with or without stabilizers.

The present invention also provides novel methods of administeringcompositions and formulations of the present invention to mammals. Themethods provide compositions of active compounds that, if presented inpresently available forms, may result in toxicity to the treated mammal.Thus, the formulations and methods of the present invention enable oneto administer compounds that previously have not been able to be widelyused in particular species due to safety considerations. The methodsalso enable one to extend the release times of compounds and provide acontrolled dose of active compound to the treated patient. The methodsof the present invention enable one to administer the pharmacologicallyactive compound to the treated mammal in a pharmaceutically effectiveamount for 4-15 days, including any specific number of days up to andincluding 15 days, or even more. The precise time will depend on severalvariables that may be manipulated to optimize the present invention fora particular pharmacologically active compound or application.Preferably the compound is present in the treated tissue 4-5 days afterinjection; and more preferably the compound is present in the treatedtissue in a pharmaceutically effective amount 6 days, or even 7 daysafter injection. In other embodiments, it may also be desirable tomanipulate variables so as to extend release times even further than 15days.

In one aspect, the present invention provides compositions foradministration of pharmacologically active compounds. The compositionsmay comprise a salt of the pharmacologically active compound with alipophilic counterion and a pharmaceutically acceptable water solublesolvent, combined together under conditions to form an injectablecomposition. The composition may precipitate and release thepharmacologically active compound over time when injected into themammal. In various embodiments, the composition of the present inventionmay comprise a wide variety of pharmacologically active compounds suchas tilmicosin, oxytetracycline, doxycycline, metoprolol, sulfamethazine,trimethoprim, neomycin, streptomycin, gentamycin, dibucaine,bupivacaine, benzocaine, tetracaine, acepromazine, itraconazole,tetracyclines, sulfonamides, aminoglycosides, or any pharmacologicallyactive compound with appropriate solubility and chemicalfunctionalities. The lipophilic counterion may be a saturated orunsaturated fatty acid of any specific number of carbons between 8 and22, preferably a C₈-C₁₈ fatty acid, and more preferably a C₁₀-C₁₈ fattyacid, such as lauric acid, linoleic acid, decanoic acid, and myristicacid. Other lipophilic counterions may also be used, for exampledicarboxylic acids, such as sebacic acid, polymeric acids, such aslipophilic poly-carboxylic acids, and aromatic acids, such as benzoicacid. The pharmaceutically acceptable carrier may be an organic solvent.In preferred embodiments, the solvent may be pyrrolidone, N-methylpyrrolidone, polyethylene glycol, propylene glycol, glycerol formal,isosorbid dimethyl ether, ethanol, dimethyl sulfoxide,tetrahydrofurfuryl alcohol, triacetin, or any combination of these, oranother solvent found to have similar acceptable properties such asbeing non-toxic and soluble in water.

In another embodiment the compositions of the invention are a salt of apharmacologically active compound with a polycarboxylic acid counterionand a pharmaceutically acceptable water soluble solvent, combinedtogether under conditions to form an injectable composition thatprecipitates when injected into water at room temperature orprecipitates in physiological (“in vivo”) environments. The compositionreleases the active compound over time when injected into a mammal. By“polycarboxylic acid” is meant a molecule containing at least twocarboxyl groups. In preferred embodiments the polycarboxylic acid ispolyaspartic acid, polyacrylic acid, sebacic acid, polysebacic acid,polybenzoic acid, or combinations thereof. By “poly” is meant two ormore.

In one embodiment, the pharmacologically active compound may beoxytetracycline, the lipophilic counterion may be lauric acid, and thepharmaceutically acceptable solvent may be propylene glycol,polyethylene glycol, glycerol formal, or an appropriate combination ofthese. In another embodiment the pharmacologically active compound maybe tilmicosin, the lipophilic counterion may be lauric acid, and thepharmaceutically acceptable solvent may be propylene glycol,polyethylene glycol, glycerol formal, or an appropriate combination ofthese. In still another embodiment, the compositions may precipitate andrelease the active compound over time when introduced or injected intoan aqueous environment. The compositions may also form a drug depot inthe mammal when injected, which releases the compound over time.

In another aspect, the present invention provides methods ofadministering a pharmacologically active compound to a mammal. Themethods may comprise preparing a composition of a salt of thepharmacologically active compound with a lipophilic counterion, and apharmaceutically acceptable water soluble solvent, combined togetherunder conditions to form an injectable formulation, and injecting thecomposition into the mammal. At least a portion of the compositionprecipitates and releases the pharmacologically active compound overtime when injected into the mammal.

In another aspect, the present invention provides methods of extendingthe release time of a pharmacologically active compound administered toa mammal. The methods may comprise preparing a formulation of a salt ofthe pharmacologically active compound with a lipophilic counterion, anda pharmaceutically acceptable water soluble solvent, combined togetherunder conditions to form an injectable formulation, and injecting thecomposition into the mammal, at least a portion of the compositionprecipitating and releasing the pharmacologically active compound overtime after injection into the mammal, thereby extending the release timeof the compound. The invention may therefore provide a controlled dosageof active compound to the treated mammal.

In yet another aspect, the present invention provides methods ofmanufacturing an injectable formulation for the administration of apharmacologically active compound to a mammal. The methods may compriseforming a salt of the pharmacologically active compound with alipophilic counterion, providing water soluble pharmaceuticallyacceptable solvent, combining the salt and the solvent under conditionsto form an injectable formulation, wherein at least a portion of theformulation precipitates and releases the pharmacologically activecompound over time when injected into the mammal.

In another aspect the present invention provides compositions for theadministration of a pharmacologically active compound to a mammal. Thecompositions contain a salt of the pharmacologically active compoundwith a lipophilic counterion and a pharmaceutically acceptable solvent,combined together to form an injectable composition. At least a portionof the pharmaceutically active compound with lipophilic counteriondissolved in the solvent precipitates in vivo and releases the activecompound over time when injected into the mammal.

The present invention therefore offers important advantages overformulations previously available. The present invention allows for thecontrolled release of pharmacologically active compounds to reducetoxicity, particularly in small animals such as dogs and cats. It alsooffers the advantage of being able to administer compounds to domesticanimals in an efficient manner, thereby requiring a smaller investmentin time and resources than is available with previous modes of drugadministration. The pharmacologically active compound is available in astable, injectable, formulation that precipitates when injected andslowly releases the active compound over an extended period of time.

The summary of the invention described above is not limiting and otherfeatures and advantages of the invention will be apparent from thefollowing detailed description of the preferred embodiments, as well asfrom the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graphical illustration showing that oxytetracycline preparedaccording to the present invention is released into saline at a rateslower than that of the free drug. The solvent is DMSO, and thelipophilic counterion is lauric acid.

FIG. 2 is a graphical illustration showing that metoprolol preparedaccording to the present invention is released into saline at a rateslower than that of the free drug. Fatty acid and solvent are lauricacid and N-methylpyrrolidone.

FIG. 3 is a graphical depiction illustrating that the rate of release ofthe pharmacologically active compound (tilmicosin) is affected by thechain length of the fatty acid selected. Solvent: N-methyl pyrrolidone;lipophilic counterion: decanoic acid and lauric acid.

FIG. 4 is a graphical depiction illustrating the solvent effect on invitro release kinetics in tilmicosin. Lipophilic counterion:di(decanoic) acid; tilmicosin at 100 mg/ml in the formulation.Abbreviations are as follows: PEG=polyethylene glycol,THFA=tetrahydro-furfuryl alcohol, DMA=dimethyl acetamide,ISO-DME=isosorbid dimethyl ether, DMSO=dimethyl sulfoxide, NMP=N-methylpyrrolidone.

FIG. 5 is a graphical depiction illustrating that the rate of release ofthe pharmacologically active compound (tilmicosin) is a function of theconcentration of fatty acid salt. Lipophilic counterion: decanoic acid.

FIG. 6 is a graphical depiction illustrating the in vitro releasekinetics of fluoxetine:lauric acid fatty acid salt formulation.

FIG. 7 is a graphical depiction of the pharmacokinetics of fluoxetinehydrochloride (HCl) and fluoxetine:lauric acid fatty acid salt (FAS) incats.

FIG. 8 is a semilog plot of tilmicosin concentration in cat lung tissueover 21 days. Eight male and eight female cats were used and dosed with10 mg/kg of body weight for all tissue types.

FIG. 9 is a semilog plot of tilmicosin concentration in cat kidneytissue over 21 days. Eight male and eight female cats were used anddosed with 10 mg/kg of body weight for all tissue types.

FIG. 10 is a semilog plot of tilmicosin concentration in cat livertissue over 21 days. Eight male and eight female cats were used anddosed with 10 mg/kg of body weight for all tissue types.

DETAILED DESCRIPTION OF THE INVENTION

The compositions of the present invention may be prepared using salts ofpharmacologically active compounds with basic functionalities. These canbe made using a variety of lipophilic acids, saturated or unsaturatedfatty acids, cholic acids, phosphatidic acids, dicarboxylic acids suchas sebacic acid or any acid that, when combined with thepharmacologically active compound, renders the resulting salt insolublein water, but soluble in a water soluble solvent. By “salt” is meant twocompounds that are not covalently linked but are chemically boundthrough ionic attractions. By “water miscible” is meant that the solventis capable of mixing in any ratio in water without separation of twophases. By “water soluble” is meant that the solvent has somesignificant level of solubility in aqueous solutions, e.g., triacetin isconsidered a water soluble solvent since it is soluble in water at aratio of about 1:14. By a “lipophilic counterion” is meant an ionic formof a fat soluble molecule. The lipophilic counterion may preferably be afatty acid, but may also be another fat soluble molecule. The counterionhas at least one charge opposite to that of a chemical group on anopposing salt member, thereby causing an ionic attraction between thetwo molecules. By “injectable formulation” or “injectable composition”is meant a formulation or composition that can be drawn into a syringeand injected subcutaneously, intraperitoneally, or intra-muscularly intoa mammal without causing adverse effects due to the presence of solidmaterials in the composition. Solid materials include, but are notlimited to, crystals, a gummy mass, and a gel. By “pharmacologicallyactive compound” is meant a chemical compound that causes apharmacological effect in the treated mammal. For example, the effectmay be to destroy or prevent growth of bacteria or parasites, reduceinflammation, or another pharmaceutical and measurable effect in thetreated mammal.

By the verb “precipitate” is meant that the compound forms aprecipitate, or solid. A precipitate is an insoluble solid formed insolution at room temperature in vitro or in a physiological (in vivo)environment. The precipitate can take many forms such as, for example, asolid, a crystal, a gummy mass, or a gel. By “pharmaceutically effectiveamount” is meant an amount that exerts a measurable and medicallysignificant effect on the treated mammal, resulting in progress towardscuring or preventing the subject disease, or alleviating or preventingthe condition that was the reason for treatment. A “pharmaceuticallyacceptable solvent” is a liquid that dissolves a salt of thepharmacologically active compound and a lipophilic counterion, and thatis suitable for use with humans and/or animals without undue adverseside effects (such as toxicity, irritation, and allergic response)commensurate with a reasonable benefit/risk ratio.

The compositions of the present invention offer several advantages. Thecompositions are injectable compositions that contain highconcentrations of the active compound. In preferred embodiments, thepharmacologically active compound may be loaded into the composition inthe range of 10%-60% (w/v). But the person of ordinary skill in the artwill realize this range may be varied widely, depending on thesolubility or insolubility of the pharmacologically active compound, thelipophilic counterion selected, the solvent selected, the injectabilityof the final product, and any other relevant needs of the particularapplication. Active compound may also be loaded as low as 10%, or 5%, oreven 1% and still provide a useful effect. Similarly, active compoundmay be loaded at 70%, or even higher as needs require. No exoticexcipients or carriers are required. The compositions are easilyfiltered, thereby simplifying the manufacturing process. It is believedthat the exclusion of water from the formulation should impart greaterstability to the formulations, and inhibit the growth of microorganisms.The processes for preparing the compositions, as described herein, aresimple, and administration according to the present invention shouldresult in milder reactions at the injection site due to theneutralization of the pharmacologically active compound.

The present invention provides the ability to modulate the release rateand release time of the pharmacologically active compound. The releaserate may be modulated by varying the lipophilicity and molecular weightof the counter-ion used to make the salt. For example, lauric acid saltsof tilmicosin are usually released more slowly than decanoate salts. Inaddition, higher concentrations of the salt in the formulation usuallyyield slower release rates. The decanoate salt of tilmicosin is releasedmore slowly from a 60% tilmicosin-fatty acid salt formulation that froma 30% tilmicosin-fatty acid salt formulation. Similarly, as explainedherein, other variables such as selection of lipophilic counterion,solvent selection, salt concentration, and others may be manipulated tolengthen or shorten the release time of the active compound to thedesired point. Generally, it may be desirable for salts to be based onthe molar ratio of charged groups. But one may also successfully createinsoluble salts by utilizing a hemi-salt or by otherwise varying from a1:1 ratio. The pharmaceutically acceptable solvent may be a watermiscible or water soluble solvent, and preferably may be a watermiscible solvent. Mixtures of water soluble and/or water misciblesolvents may also be utilized. The person of ordinary skill in the artwill realize that various water soluble solvents may be mixed tooptimize the result for a particular application. For example, a mixtureof polyethylene glycol, propylene glycol, and glycerol formal may bemixed in various ratios to provide an optimal solvent. In someembodiments, mixing in approximately even amounts may provide a suitablesolvent.

In other embodiments, formulations of the invention containing a salt ofthe pharmacologically active compound with a lipophilic counterion canbe combined with the unsalted form of the active, in order to provide agreater initial dose of active compound.

Without wanting to be bound by any particular theory, injectablecompositions may be obtained when a salt is formed of apharmacologically active agent with a lipophilic counterion, andcombined with a parenteral organic solvent. It is believed that whenthis formulation is injected into a mammal, the solvent may diffuse awayfrom the injection site as aqueous body fluids diffuse towards the site,resulting in the precipitation of the pharmacologically active compoundin the treated mammal. The precipitate may take many forms, for example,a solid, crystals, a gummy mass, or a gel. There will thus exist aconcentration of the active compound that is released in apharmaceutically effective amount over a desired period of time. Theprecipitate may act as a drug depot in the mammal resulting in therelease of the compound over a period of time. Release times may beobtained of at least 3 days, at least 4 days, at least 5 days, at least6 days at least 7 days, or any specific number of days up to andincluding at least 15 days, or even longer, as desired. By “drug depot”is meant a concentration or precipitation of pharmacologically activecompound within the body of the treated mammal that releases apharmaceutically effective amount of the active compound over time.

It was shown that the fatty acid chain length, the particularcombinations of fatty acids, the percent pharmacologically activecompound:lipophilic counterion salt in the formulation, and thepharmaceutically acceptable solvent selected all influence the releasekinetics of the pharmacologically active compound. Thus, the releasekinetics of the pharmacologically active compound may be convenientlyand easily managed by manipulating these and other variables. It wasalso found that the formulations were stable to being sterilized byautoclave. The person of ordinary skill in the art will realize that thepresent invention may be applied to many pharmacologically activecompounds that have an appropriate solubility and chemicalfunctionality. Thus, it is contemplated that the present invention maybe applicable to a wide variety of pharmacologically active compounds,such as drugs, medications, nutrients, or other desirable compounds foradministration to a mammal.

The person of ordinary skill in the art will realize that somemodifications to the methods presented herein may be desirable based onthe particular characteristics of the pharmacologically active compoundinvolved. The following non-limiting examples present furtherapplications of the present invention and are provided by way of exampleonly.

EXAMPLE 1 Oxytetracycline

Oxytetracycline has one tertiary amine group, and the hydrochloride saltof oxytetracycline is readily soluble in water. We have found thatadding one mole of fatty acids to one mole of oxytetracycline creates asalt that has lower solubility in water but is more soluble than thestarting oxytetracycline in N-methylpyrrolidone (NMP). When water isadded to the NMP formulation, the salt precipitates.

The in vitro rate of release of oxytetracycline may be determined bysealing the formulation in a dialysis bag (Pierce, Rockford, Ill.),placing it in a reservoir of saline solution, and measuring the amountof drug in the saline as a function of time. The formulation of thepresent invention was compared with existing oxytetracyclineformulations. FIG. 1 shows that the oxytetracycline formulation of thepresent invention is released into the saline at a rate substantiallyslower than that of the free drug.

An oxytetracycline composition according to the present invention wasprepared by adding 0.464 grams of oxytetracycline and 0.203 grams oflauric acid to 3 ml of NMP. The mixture was stirred for 60 minutes,resulting in a clear solution. 1 ml of this solution was sealed in adialysis bag, and the bag was suspended in 150 ml of phosphate-bufferedsaline, pH 7.4. Aliquots were removed at various intervals andoxytetracycline concentration was determined by spectrophotometry. Theresults in FIG. 1 show that oxytetracycline continued to diffuse out ofthe bag for more than 120 hours, at which point only about 50% of theoxytetracycline present had been released.

EXAMPLE 2 Metoprolol

Metoprolol is an antihypertensive, antianginal and antiarrhythmic drug,of the following structure:

Its succinate and tartarate salts are available commercially underseveral trade names. Both these salts as well as the baseform of thedrug-are highly soluble in water. The base form of the metoprolol wasprepared from commercially available tartarate salt by standardprocedure. When the amine group of metoprolol is neutralized with lauricacid, the resulting salt is poorly soluble in water, but readily solublein pharmaceutically-acceptable non-aqueous solvents. A metoprololcomposition according to the present invention was prepared by adding0.3224 grams of metoprolol base and 0.2661 grams of lauric acid to 2.415ml of NMP. The mixture was stirred for 30 minutes, resulting in a clearsolution. One ml of this solution was sealed in a dialysis bag, and thebag was suspended in 150 ml of phosphate-buffered saline, pH 7.4.Aliquots were removed at various intervals and metoprolol concentrationwas determined by spectrophotometry. The results in FIG. 2 show thatmetoprolol continued to diffuse out of the bag for more than 48 hourswhile the control solution of metoprolol base (prepared by dissolving150 mg in 1.124 ml of NMP) is diffused off rapidly.

EXAMPLE 2A Tilmicosin

Tilmicosin is an antibiotic in the macrolide class with the followingstructure:

It is effective against a broad range of bacteria, and is used for thetreatment of respiratory diseases in cattle. The basic form ismoderately soluble in aqueous solutions, while the chloride andphosphate salts are highly soluble. At elevated levels, tilmicosin iscardiotoxic, and therefore is not administered intravenously. For safetyreasons, its use has been avoided almost entirely in sensitive speciessuch as cats, goats, pigs, and horses.

When the two amine groups of tilmicosin are neutralized with any ofseveral fatty acids (such as, for example, decanoic C₁₀, lauric C₁₂,myristic C₁₄, palmitic C₁₆, stearic C₁₈, Oleic C₁₈, elaidic C₁₈,linoleic C₁₈, and erucic C₂₂), the resulting salt is poorly soluble inwater, but readily soluble in pharmaceutically-acceptable non-aqueoussolvents. When the formulation of the salt is sealed in a dialysiscassette and place in saline, the tilmicosin salt precipitates, andtilmicosin is slowly released from the bag. The rate of release is afunction of the chain length of the fatty acid (FIG. 3), the solvent(FIG. 4) and the tilmicosin-fatty acid salt concentration (FIG. 5).

EXAMPLE 3 Tilmicosin Salts in vitro

10 grams (0.0115 moles) of tilmicosin and 0.0253 moles of variouscarboxylic acids (such as, for example, decanoic, lauric, linoleic, ormyristic acids, in individual assays) were taken in a flask and made upto a final volume of 100 ml with N-methyl-pyrrolidone and stirred for 60minutes to obtain a clear solution. One ml aliquots of these solutionswere sealed in dialysis bags, and the bags were suspended in flaskscontaining 150 ml of phosphate-buffered saline, pH 7.4. The salt wasobserved to precipitate in the bag within about 1 hour. Aliquots ofsaline were removed at various intervals and tilmicosin was determinedby HPLC. The results with decanoic acid (C-10) and lauric acid (C-12)salts in FIG. 3 show that tilmicosin continued to diffuse out of the bagfor more than 120 hours. Longer chain length acids caused a slowerrelease of tilmicosin. Micotil® (Eli Lilly, Indianapolis, Ind.), aphosphate salt of tilmicosin, is readily soluble and rapidly diffusesfrom the bag.

EXAMPLE 4 Tilmicosin-di(Decanoic Acid) in Various Solvents

Solutions of tilmicosin di(decanoic acid) salt were prepared in severalwater-miscible solvents, combining 10 grams (0.0115 moles) of tilmicosinand 0.0253 moles of decanoic acid in various solvents to a final volumeof 100 ml. The in vitro release rates were measured using the dialysismethod of Example 1. The results in FIG. 4 show that the release ratevaries with the solvent, but that all of the solvents yield a slowerrelease rate than that observed with the phosphate salt (Micotil (R))shown in FIG. 3.

EXAMPLE 5 Tilmicosin Release Concentration Effect

Solutions of tilmicosin di(decanoic acid) salt were prepared bycombining 30 grams (0.0345 moles) or 60 grams (0.0690 moles) oftilmicosin with 2 equivalents of decanoic acid in NMP to a final volumeof 100 ml. The in vitro release rates were measured using the dialysismethod of Example 1, and the data in FIG. 5 show that higher startingconcentrations result in a slower release rate.

EXAMPLE 6 Tilmicosin in vivo

Formulations of tilmicosin didecanoate, dilaurate, and dimyristate wereformulated at 100 mg/ml in N-methyl pyrrolidone and subcutaneouslyinjected into cats in the back of the neck at a dosage of 45 or 75 mg/kgof body weight. Previous data indicates that a dosage of 25 mg/kg of thephosphate salt of tilmicosin is fatal to cats. The cats showedhypothermia and lethargy after injection, indicative of thebioavailability of the drug. The toxicity was found to be substantiallyless in formulations with fatty acid chain lengths greater than C₁₀,consistent with the slower release of drug from these formulations. Allof the cats survived and were behaving normally 3 days after theinjection. The results are summarized in the following Table 1.

TABLE 1 Blood levels of Tilmicosin at Specific Time Intervals 100 mg/mlof a formulation of a salt of tilmicosin with decanoic acid, lauricacid, or myristic acid in N-methyl pyrrolidone were injected into 9healthy adult cats at the dosages indicated. The resultingconcentrations in blood cells and plasma for each individual cat at 6hours and 2 days are shown in Table 1. 6 hrs 6 hrs Day 2 Day 2 Cat FattyBlood cells Plasma Blood cells Plasma No. Acid Dosage (μg/ml) (μg/ml)(μg/ml) (μg/ml) 1 C-12 45 mg/kg 5.8 11.3 0.9 0.5 2 C-12 75 mg/kg 5.518.0 1.5 1.5 3 C-12 75 mg/kg 2.5 9.9 0.9 1.0 4 C-14 45 mg/kg 2.4 7.5 0.91.1 5 C-14 75 mg/kg 6.7 11.6 9.1 4.6 6 C-14 75 mg/kg 3.5 6.1 1.5 0.7 7C-10 45 mg/kg 3.7 15.9 8 C-10 75 mg/kg 4.2 18.4 9 C-10 45 mg/kg 3.3 9.1

Tilmicosin salts were also studied in tissue. A tilmicosin:dilauricfatty acid salt in 10% propylene glycol in glycerol formal at 100 mg/mlwas administered subcutaneously at 10 mg/kg dose and the biodistributionin cats was determined.

The methods described here were developed for the determination andquantification of tilmicosin in various animal tissues and serum,particularly feline liver, kidney and lung tissue and serum. The personof ordinary skill in the art will realize that many variations of themethods described here are possible without departing from theinvention.

The kidney, liver and lung tissue samples were collected 2, 3, 4, 7, 14,and 21 days after injecting the animals with tilmicosin formulation at10 mg/kg of body weight. The results are presented in FIGS. 8, 9 & 10.It was found that kidney is the marker tissue in cats while the liver isthe marker in cows and pigs. The levels in kidney were consistentlyhigher than in liver with Cmax (kidney: 13.8 mcg/gm; Liver: 7.3 mcg/gm)reached around 48 hours in both tissues. The Cmax for lung was found tobe 7.5 mcg/gm and was observed around 48 hours after injecting the dose.Detectable levels of tilmicosin persisted in tissues through day 21 ofthe study.

A drug extraction efficiency of ˜98% was obtained at a concentration of1 mcg/gm of tissue. The limit of detection for tilmicosin in variousfeline tissues was determined to be 0.032 mcg/gm. For feline serum, adrug extraction efficiency of 95% was obtained over a concentrationrange of 0.15 to 6 mcg/ml after fortification. The limit of detectionwas determined to be 0.16 mcg/ml with linearity extending from 0.15 to 6mcg/ml.

Preparation of Tissue Samples

Tissue samples were prepared by mincing with scissors or a scalpel on apaper towel. 10 ml of methanol was added to each tube and the sampleshomogenized separately for 10 to 15 minutes. Samples were sonicated onice for one minute and centrifuged at 10,000 rpm for 30 minutes at 4 C.The methanol extract was decanted into fresh centrifuge tubes and thetissue samples resuspend in the tubes with 10 mL of methanol and 5.0 mLof 100 mM phosphate. The tubes were vortexed and centrifuged at 10,000rpm for 30 minutes at 4 C. The extract was decanted into freshcentrifuge tubes and centrifuged at 5000 rpms for 10 minute at 4 C. Themethanol extract was added to 70 mL of water in a flask and swirled inthe flask to mix.

Each pool of extracts was loaded to a solid phase extraction C₁₈ Sep-PakPlush® (SPE) cartridge (Waters, Milford, Mass.) using a vacuum manifoldor hydrostatic pump to draw the pools through the cartridges. Oncesample were completely loaded, each SPE cartridge was washed with 10 mLof water, and then with 10 mL of 25% acetonitrile/water at a flow rateof less than 5 mL/minute. The SPE cartridges were disconnected from theapparatus and dried completely under high vacuum (26 in. Hg) in a vacuumdesiccation jar for 10 minutes.

Analyte was eluted from the SPE cartridges with 5% acetic acid/methanol.Only the first 2.0 mL of eluate was collected. The volumetric flaskswere inverted and mixed, and stored overnight at 4 C.

The sample eluates were filtered through a 0.22 um PVDF filter, andanalyzed by HPLC on a SphereClone® 5 um phenyl column (Phenomenex,Torrance, Calif.).

EXAMPLE 7 Fluoxetine

Fluoxetine is a selective serotonin reuptake inhibitor and isextensively used to treat psychological disorders such asobsessive-compulsive disorder in humans. It is shown that fluoxetine iseffective for treating aggressive behavior and separation anxiety indogs and urine spraying behavior in cats. Fluoxetine is formulated at100 and 150 mg/ml as a lauric acid salt in 10% propylene glycol inglycerol formal in 1:1 drug to fatty acid ratio. In vitro releasekinetics were studied for both formulations at 100 mg/mL concentrationusing the dialysis technique described in Example 1, and the resultspresented in FIG. 6. Fluoxetine base in 10% propylene glycol in glycerolformal at 100 mg/ml is used as a control in the experiment. While thefluoxetine base formulation is released for about 160 hrs, the 1:1(drug:LA) lauric acid salt formulation was released for 700 hrs.

The fatty acid salt formulation with 1:1.1 fluoxetine to lauric acidratio at 150 mg/mL concentration was injected sub cutaneous into cats at20 and 30 mg/kg. At the same time two cats were dosed at 1 mg/kg/dayorally for 28 days. Serum samples were collected through day 42 andanalyzed for fluoxetine by HPLC using 35% acetonitrile in phosphatebuffer, pH 2.7 on a C₁₈ column. The results suggest that a singlesubcutaneous injection of fatty acid salt formulation provide drugconcentrations comparable to daily oral dose through 42 days (FIG. 7).

The fluoxetine was also formulated as linoleic acid salt in 10%propylene glycol in glycerol formal, yielding a clear solution. Thisformulation was also found to precipitate in water.

EXAMPLE 8 Roxithromycin

Roxithromycin is an antibiotic in the macrolide class with the followingstructure:

It is effective against a broad range of bacteria, and is used for thetreatment of respiratory diseases in cattle. The amine group ofroxithromycin was neutralized with linoleic acid in 10% propylene inglycerol formal, resulting in a clear solution at 200 mg/ml. As in thecase of tilmicosin, the salt precipitated when the solution was spikedin water.

EXAMPLE 9 Turbinafine

Turbinafine is an antifungal and the structure is as shown below:

Turbinafine is a specific inhibitor of squaline epoxidase, a key enzymein fungal ergosterol biosynthesis. The amine group of turbinafine wasneutralized with linoleic acid in 10% propylene glycol in glycerolformal, resulting in a clear solution at 150 mg/ml. The resulting saltwas highly insoluble in water, and precipitated when spiked into water.

While the invention has been described and exemplified in sufficientdetail for those skilled in this art to make and use it, variousalternatives, modifications, and improvements should be apparent withoutdeparting from the spirit and scope of the invention.

One skilled in the art readily appreciates that the present invention iswell adapted to carry out the objects and obtain the ends and advantagesmentioned, as well as those inherent therein. Modifications therein andother uses will occur to those skilled in the art. These modificationsare encompassed within the spirit of the invention and are defined bythe scope of the claims.

It will be readily apparent to a person skilled in the art that varyingsubstitutions and modifications may be made to the invention disclosedherein without departing from the scope and spirit of the invention.

All patents and publications mentioned in the specification areindicative of the levels of those of ordinary skill in the art to whichthe invention pertains.

The invention illustratively described herein suitably may be practicedin the absence of any element or elements, limitation or limitationswhich is not specifically disclosed herein. The terms and expressionswhich have been employed are used as terms of description and not oflimitation, and there is no intention that in the use of such terms andexpressions of excluding any equivalents of the features shown anddescribed or portions thereof, but it is recognized that variousmodifications are possible within the scope of the invention claimed.Thus, it should be understood that although the present invention hasbeen specifically disclosed by preferred embodiments and optionalfeatures, modification and variation of the concepts herein disclosedmay be resorted to by those skilled in the art, and that suchmodifications and variations are considered to be within the scope ofthis invention as defined by the appended claims.

In addition, where features or aspects of the invention are described interms of Markush groups, those skilled in the art will recognize thatthe invention is also thereby described in terms of any individualmember or subgroup of members of the Markush group. For example, if X isdescribed as selected from the group consisting of bromine, chlorine,and iodine, claims for X being bromine and claims for X being bromineand chlorine are fully described.

Other embodiments are set forth within the following claims.

1. A composition for administration of a pharmacologically activecompound to a mammal, comprising: a salt of the pharmacologically activecompound with a lipophilic counterion; and a pharmaceutically acceptablesolvent; combined together to form an injectable composition thatprecipitates when injected into water; and wherein the compositionreleases the active compound over time when injected into the mammal. 2.The composition of claim 1 wherein the pharmaceutically acceptablesolvent is a water miscible solvent.
 3. The composition of claim 1wherein the pharmacologically active compound is an antibiotic.
 4. Thecomposition of claim 1 wherein the pharmacologically active compound istilmicosin, oxytetracycline, doxycycline, fluoxetine, roxithromycin,terbinafine or metoprolol.
 5. The composition of claim 1 wherein thepharmacologically active compound is selected from the group consistingof: trimethoprim, neomycin, streptomycin, gentamycin, dibucaine,bupivacaine, benzocaine, tetracaine, acepromazine, itraconazole,tetracyclines, sulfonamides, and aminoglycosides.
 6. The composition ofclaim 1 wherein the lipophilic counterion is a C₁₀-C₂₂ saturated orun-saturated fatty acid.
 7. The composition of claim 1 wherein thelipophilic counterion is a C₁₀-C₁₅ saturated or unsaturated fatty acid.8. The composition of claim 7 wherein the fatty acid selected from thegroup consisting of: lauric acid, decanoic acid, myristic acid, oleicacid and linoleic acid.
 9. The composition of claim 1 wherein thelipophilic counterion is a polycarboxylic acid.
 10. The composition ofclaim 9 wherein the polycarboxylic acid is selected from the groupconsisting of: sebacic acid, polysebacic acid, polyaspartic acid,polyacrylic acid, and polybenzoic acid.
 11. The composition of claim 1wherein the pharmaceutically acceptable solvent is selected from thegroup consisting of one or a combination of: pyrrolidone, N-methylpyrrolidone, polyethylene glycol, propylene glycol, glycerol formal,isosorbide dimethyl ether, ethanol, dimethyl sulfoxide, andtetrahydrofurfuryl alcohol.
 12. The composition of claim 1 wherein thepharmaceutically acceptable solvent comprises 10% propylene glycol inglycerol formal with or without stabilizers.
 13. The composition ofclaim 1 wherein the pharmaceutically acceptable solvent is triacetin.14. The composition of claim 1 wherein the pharmacologically activecompound is oxytetracycline, the lipophilic counterion is lauric acid,and the pharmaceutically acceptable solvent is selected from the groupconsisting of one or more of polyethylene glycol, propylene glycol, andglycerol formal.
 15. The composition of claim 1 wherein thepharmacologically active compound is tilmicosin, the lipophiliccounterion is lauric acid, and the pharmaceutically acceptable solventis selected from the group consisting of one or more of polyethyleneglycol, propylene glycol, and glycerol formal.
 16. A method ofadministering a pharmacologically active compound to a mammalcomprising: preparing a composition comprising a salt of thepharmacologically active compound and a lipophilic counterion; and apharmaceutically acceptable solvent; combined together to form aninjectable formulation; and injecting the composition into the mammal;wherein at least a portion of the composition precipitates and releasesthe active compound over time when injected into the mammal.
 17. Themethod of claim 16 wherein the pharmaceutically acceptable solvent is awater miscible solvent.
 18. The method of claim 16 wherein thepharmacologically active compound is an antibiotic.
 19. The method ofclaim 18 wherein the antibiotic is tilmicosin, tetracycline, ordoxycycline.
 20. The method of claim 18 wherein the antibiotic isselected from the group consisting of: trimethoprim, neomycin,streptomycin, gentamycin, tetracyclines, sulfonamides, andaminoglycosides.
 21. The method of claim 16 wherein the lipophiliccounterion is a fatty acid.
 22. The method of claim 21 wherein the fattyacid is a C₁₀-C₂₂ fatty acid.
 23. The method of claim 22 wherein thefatty acid is selected from the group consisting of: lauric acid,decanoic acid, myristic acid, oleic acid and linoleic acid.
 24. Themethod of claim 16 wherein the lipophilic counterion is sebacic acid.25. The method of claim 16 wherein the pharmaceutically acceptablesolvent is selected from the group consisting of: pyrrolidone, N-methylpyrrolidone, polyethylene glycol, propylene glycol, glycerol formal,isosorbide dmethyl ether, ethanol, dimethyl sulfoxide, andtetrahydrofurfuryl alcohol.
 26. The method of claim 16 wherein thepharmaceutically acceptable solvent is triacetin.
 27. The method ofclaim 16 wherein the pharmacologically active compound isoxytetracycline, the lipophilic counterion is lauric acid, and thepharmaceutically acceptable solvent is selected from the groupconsisting of one or more of polyethylene glycol, propylene glycol, andglycerol formal.
 28. The method of claim 16 wherein pharmacologicallyactive compound is tilmicosin, the lipophilic counterion is decanoicacid, and the pharmaceutically acceptable solvent is selected from thegroup consisting of one or more of polyethylene glycol, propyleneglycol, and glycerol formal.
 29. A method of extending the release timeof a pharmacologically active compound administered to a mammalcomprising, preparing a formulation comprising, a salt of thepharmacologically active compound and a lipophilic counterion; and apharmaceutically acceptable solvent; combined together to form aninjectable formulation; and injecting the formulation into the mammal;wherein at least a portion of the formulation precipitates and releasesthe active compound over time when injected into the mammal, therebyextending the release time of the pharmacologically active compound. 30.The method of claim 29 wherein the pharmaceutically acceptable solventis a water miscible solvent.
 31. The method of claim 29 wherein thelipophilic counterion is a C₁₀-C₁₈ fatty acid.
 32. The method of claim31 wherein the antibiotic is tilmicosin, oxytetracycline, ordoxycycline.
 33. The method of claim 32 wherein the fatty acid selectedfrom the group consisting of: lauric acid, decanoic acid, and myristicacid.
 34. The method of claim 29 wherein the lipophilic counter ion issebacic acid.
 35. The method of claim 29 wherein the pharmacologicallyactive compound is oxytetracycline, the lipophilic counterion is lauricacid, and the pharmaceutically acceptable solvent is selected from thegroup consisting of one or more of polyethylene glycol, propyleneglycol, and glycerol formal.
 36. The method of claim 29 wherein thepharmacologically acceptable compound is tilmicosin, the lipophiliccounterion is lauric acid, and the pharmaceutically acceptable solventis selected from the group consisting of one or more of polyethyleneglycol, propylene glycol, and glycerol formal.
 37. A method ofmanufacturing an injectable formulation for the administration of apharmacologically active compound to a mammal comprising, providing asalt of the pharmacologically active compound with a lipophiliccounterion; providing a pharmaceutically acceptable solvent; combiningthe salt and the solvent to form an injectable formulation; wherein atleast a portion of the formulation precipitates and releases the activecompound over time when injected into the mammal.
 38. The method ofclaim 37 wherein the pharmaceutically acceptable solvent is a watermiscible solvent.
 39. The method of claim 37 wherein thepharmacologically active compound is an antibiotic.
 40. The method ofclaim 37 wherein the antibiotic is tilmicosin, oxytetracycline, ordoxycycline.
 41. The method of claim 37 wherein the lipophiliccounterion is a C₁₀-C₁₈ fatty acid.
 42. The method of claim 41 whereinthe fatty acid is selected from the group consisting of: lauric acid,decanoic acid, and myristic acid.
 43. The method of claim 37 wherein thelipophilic counterion is sebacic acid.
 44. The method of claim 37wherein the pharmaceutically acceptable solvent is selected from thegroup consisting of: pyrrolidone, N-methyl pyrrolidone, polyethyleneglycol, propylene glycol, glycerol formal, isosorbide dimethyl ether,ethanol, dimethyl sulfoxide, and tetrahydrofurfuryl alcohol.
 45. Themethod of claim 37 wherein the pharmaceutically acceptable solvent istriacetin.
 46. The method of claim 37 wherein the pharmacologicallyactive compound is oxytetracycline, the lipophilic counterion is lauricacid, and the pharmaceutically acceptable solvent is selected from thegroup consisting of one or more of polyethylene glycol, propyleneglycol, and glycerol formal.
 47. The method of claim 37 wherein thepharmacologically active compound is tilmicosin, the lipophiliccounterion is lauric acid, and the pharmaceutically acceptable solventis selected from the group consisting of one or more of polyethyleneglycol, propylene glycol, and glycerol formal.
 48. A composition foradministration of a pharmacologically active compound to a mammal,comprising: a salt of the pharmacologically active compound with alipophilic counterion; and a pharmaceutically acceptable solvent;combined together to form an injectable composition; and wherein atleast a portion of the composition precipitates and releases the activecompound over time when injected into an aqueous environment.
 49. Thecomposition of claim 48 wherein the pharmaceutically acceptable solventis water miscible.
 50. The composition of claim 48 wherein theantibiotic is tilmicosin, oxytetracycline, or doxycycline.
 51. Thecomposition of claim 48 wherein the pharmacologically active compound isselected from the group consisting of: trimethoprim, neomycin,streptomycin, gentamycin, dibucaine, bupivacaine, benzocaine,tetracaine, acepromazine, itraconazole, tetracyclines, sulfonamides, andaminoglycosides.
 52. The composition of claim 48 wherein the lipophiliccounterion is a C₁₀-C₁₈ fatty acid.
 53. The composition of claim 52wherein the fatty acid selected from the group consisting of: lauricacid, decanoic acid, and myristic acid.
 54. The composition of claim 48wherein the lipophilic counterion is sebacic acid.
 55. The compositionof claim 48 wherein the pharmaceutically acceptable solvent is selectedfrom the group consisting of one or a combination of: pyrrolidone,N-methyl pyrrolidone, polyethylene glycol, propylene glycol, glycerolformal, isosorbide dimethyl ether, ethanol, dimethyl sulfoxide, andtetrahydrofurfuryl alcohol.
 56. The composition of claim 48 wherein thepharmaceutically acceptable solvent is triacetin.
 57. A composition foradministration of a pharmacologically active compound to a mammal,comprising: a salt of the pharmacologically active compound with alipophilic counterion; and a pharmaceutically acceptable solvent;combined together to form an injectable composition; and wherein atleast a portion of the pharmaceutically active compound and lipophiliccounterion dissolves in the solvent and precipitates in vivo.
 58. Acomposition for administration of a pharmacologically active compound toa mammal, comprising: a salt of the pharmacologically active compoundwith a polycarboxylic acid counterion; and a pharmaceutically acceptablesolvent; combined together to form an injectable composition thatprecipitates when injected into water; and wherein the compositionreleases the active compound over time when injected into the mammal.59. The composition of claim 58 wherein the polycarboxylic acid isselected from the group consisting of: polyaspartic acid, polyacrylicacid, sebacic acid, polysebacic acid, and polybenzoic acid.
 60. Thecomposition of claim 58 wherein the pharmaceutically acceptable solventis a water miscible solvent.
 61. The composition of claim 58 wherein thepharmacologically active compound is an antibiotic.
 62. The compositionof claim 58 wherein the pharmacologically active compound is tilmicosin,oxytetracycline, doxycycline, fluoxetine, roxithromycin, terbinafine ormetoprolol.
 63. The composition of claim 58 wherein thepharmacologically active compound is selected from the group consistingof trimethoprim, neomycin, streptomycin, gentamycin, dibucaine,bupivacaine, benzocaine, tetracaine, acepromazine, itraconazole,tetracyclines, sulfonamides, and aminoglycosides.